Zirconium alloy elements used in pressurized water reactors for nuclear power stations, in particular those used to make the cladding tubes for fuel pellets, need to present characteristics of high levels of resistance to various types of corrosion. In particular generalized corrosion in media containing lithium and media not containing lithium needs to be taken particularly into consideration.
Various solutions to this problem have been proposed.
Document EP-B1-0 840 931 proposes using quaternary alloys, i.e. alloys of zirconium containing significant quantities of three alloying elements, namely 0.8% to 1.8% niobium, 0.2% to 0.6% tin, and 0.02% to 0.4% iron (where all these percentages, are percentages by weight, as are the percentages throughout the description below).
In such alloys, the carbon content must be maintained in the range 30 parts per million (ppm) to 180 ppm, the silicon content in the range 10 ppm to 120 ppm, and the oxygen content in the range 1600 ppm to 1800 ppm. The composition may be associated with a special thermomechanical treatment method.
Document EP-B1-1 149 180 also proposes such quaternary alloys comprising 0.5% to 1.6% niobium, 0.3% to 0.6% iron, and 0.65% to 0.85% tin, possibly together with 50 ppm to 120 ppm of silicon and possibly 500 ppm to 1600 ppm of oxygen.